The Hygiene Hypothesis

Of course, it would be better if we could prevent kids from being exposed to the allergens and toxins that are setting off asthma in the first place. Imagine a world without cigarette smoke and diesel fumes for breakfast, and we’re probably halfway there. Yet according to an increasing body of thought, that same imagining of a world less prone to inflammatory disease would also encourage us to expose our toddlers to all sorts of viruses and bacteria, and to deliberately infect sensitive adults with intestinal hookworms.

The essence of this idea is embodied in “the hygiene hypothesis.” First proposed by a British physician, David Strachan, in 1989, the hygiene hypothesis suggests that a large part of the increase in allergic inflammatory diseases in the twentieth century is attributable to the unusually sanitary conditions in which we now live. The immune system requires a delicate balance of efforts to fight diverse viruses, bacteria, and parasites. This must be primed during childhood, but since infants are no longer exposed to a traditional barrage of pathogens, they don’t get the balance right. Hypersensitivity to unusual allergens follows, like weeds after a cleansing rainfall.